Bone envelope changes without reparenting
From the manual

With Envelope Weights


  Works in a similar way to With Automatic Weights. The difference is
  that the influences are calculated based on the Bone Envelopes
  settings. It will assign a weight to each vertex group the vertices
  that is inside its bone’s influence volume, depending on their
  distance to this bone.
  
  This means newly included/excluded vertices or new envelope settings
  will not be taken into account. You will have to apply Armature Deform
  With Envelope Weights parenting again.


And in particular


  Tip
  
  If you want the envelope setting to be used instantly, bind the
  Armature Modifier to Bone Envelopes.